rt8060a Richtek Technology Corporation, rt8060a Datasheet - Page 9

• Manufacturer Part Number: rt8060a
• Description: 1.5mhz, 1a High Efficiency Step-down Converter
• Manufacturer: Richtek Technology Corporation

PGOOD Output
PGOOD is an open-drain output that indicates whether
the output voltage is ready or not. PGOOD is typically
pulled up to 3.3V or tied with VIN. PGOOD is in high
impedance when the voltage on FB pin exceeds the rising
threshold 90% of V
impedance when the voltage on FB pin falls below the
falling threshold 85% of V
If the voltage detector feature is not required, connect
PGOOD to ground.
Thermal Considerations
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature. The
maximum power dissipation can be calculated by the
following formula :
P
where T
the ambient temperature, and θ
thermal resistance.
For recommended operating condition specifications of
the RT8060A, the maximum junction temperature is 125°C
and T
thermal resistance, θ
23-5 packages, the thermal resistance, θ
on a standard JEDEC 51-3 single-layer thermal test board.
The maximum power dissipation at T
calculated by the following formula :
P
SOT-23-5 package
DS8060A-00 March 2011
D(MAX)
D(MAX)
Figure 2. V
A
is the ambient temperature. The junction to ambient
= (T
J(MAX)
= (125°C − 25°C) / (250°C/W) = 0.4W for
PGOOD
85% V
J(MAX)
V
is the maximum junction temperature, T
FB
FB
REF
and PGOOD Comparator Waveform
− T
A
REF
JA
) / θ
, is layout dependent. For SOT-
0.6V (typ). PGOOD is in low
JA
REF
.
JA
is the junction to ambient
90% V
A
= 25°C can be
JA
, is 250°C/W
REF
A
is
The maximum power dissipation depends on the operating
ambient temperature for fixed T
resistance, θ
curve in Figure 3 allows the designer to see the effect of
rising ambient temperature on the maximum power
dissipation.
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
Figure 3. Derating Curves for RT8060A Package
0
JA
. For the RT8060A package, the derating
25
Ambient Temperature (°C)
50
75
RT8060A
J(MAX)
Single-Layer PCB
www.richtek.com
and thermal
100
125
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